Eve CEO Jas Bagniewski told Business Insider on Monday that its rapid revenue growth has been driven by "four main areas."

"The first one is continuing to invest in brand and marketing in the UK," he said. "In the UK we increased marketing spend by 50% in the second half over the first half. Even so, efficiency improved massively, by 15 basis points.

"The second thing is internationalisation. We rolled out to a bunch of new markets in 2017, and we're in 15 markets now.

"Thirdly, new product development and non-mattress sales, which grew a lot. We had four products at the beginning of 2017, we had 15 at the end. That sort of results in, without really any marketing, non-mattress sales becoming almost 20% of the business by the end of the year."

Eve Sleep now sells other sleep-related products such as pillows and sheets and Bagniewski said 12% of sales now come from repeat customers.

Bagniewski said: "And finally, expansion into retail. At the beginning of 2017 we were in one store and at the end, we were in 145. From Q4, retail did about £1.75 million for us."

Bagniewski said: "What we see generally is just a shift from offline to online. In the US, three years ago $300 million worth of mattresses were sold online and that was $1.2 billion in 2017. Euromonitor has our category as the second fastest shift in retail from offline to online.

"That shift is definitely happening and we think things like Warren Evans and Feather & Black are just an effect of that shift really rather than a cause of it."

Bagniewski said Eve Sleep plans to launch new products in the year ahead, including a new mattress and expanding its existing beds and sheets ranges.

"We obviously don't want to talk too much about those because we don't want to alert our competitors," he said.

Eve Sleep's share price is down 0.8% as of 11.50 a.m. GMT (7.50 a.m. ET). Bagniewski said: "Our main investors all take a long-term view.

"We do look at it, obviously, but the reality is the volume is really small, it's all retail trading. It's not something we control really. We think the results we put out are really, really strong and we think the share price will be more defined by our discussions with fund managers over the next couple of weeks rather than a bit of retail volume."